Trustworthiness is a crucial characteristic when it comes to evaluating any product, even more so for open source software, which is now becoming widely used. The authors conducted a survey to identify the reasons and motivations that lead software companies to adopt or reject open source software; they then ranked, according to importance, the specific trust factors used when selecting an open source software component or product. The motivations and importance ranking of factors might be useful for both developers of open source software (to make their products and components more useful for other stakeholders) and to future prospective open source software users.